Re: [secdir] Secdir last call review of draft-ietf-nfsv4-mv1-msns-update-04

David Noveck <davenoveck@gmail.com> Fri, 08 March 2019 23:52 UTC

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From: David Noveck <davenoveck@gmail.com>
Date: Fri, 8 Mar 2019 18:52:33 -0500
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To: Sean Turner <sean@sn3rd.com>
Cc: secdir@ietf.org, ietf@ietf.org, NFSv4 <nfsv4@ietf.org>, draft-ietf-nfsv4-mv1-msns-update.all@ietf.org
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Subject: Re: [secdir] Secdir last call review of draft-ietf-nfsv4-mv1-msns-update-04
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I previously said:
> Will address nits 0)-4) and 6)-10) in -05.

However when I looked more closely at 9), I've found that I cannot make the
requested change.

> 9) s12.2.3: replace ietf.org with example.org (not supposed to use
> real domains even if it is “ours”).

This is not an example.   The use of ietf,org is intentional and is
intended as a way
to provide the ability to define globally usable variable definition as
well as domain-specific
ones.  This is specified in section 22.5 of RFC5661.   I'm not sure about
the details of
the prohibition of the use of real domain names but I can;t see how it
would apply in this
case where this form of vatibl specification, including a real domain name
has already
been adopted.


On Thu, Feb 28, 2019 at 8:30 PM David Noveck <davenoveck@gmail.com> wrote:

> > These
> > instructions will really help when work on a fully revised NFS RFC gets
> > going.
>
> That's the intention.  The working group is now discussing the possibility
> of an rfc5661bis
> that would use those instructions.   Note that the current document would
> be the source of
> a large set of the changes but there are also others: The
> internationalization section needs to
> be updated as it was in RFC7530.  Section 12 needs to be updated to
> reflect the work done by
> RFC8434.  Also, there are a lot of erratta that would need to be applied.
>
> > 0) The big issue being addressed in the security considerations is the
> fact
> > that RPSEC_GSS is must support not must use
>
> That reflects choices made for RFC3530 and carried over until now.   This
> has resulted in
> a situation in which AUTH_SYS is very commonly used despite its obvious
> security weaknesses.
>
> > So what do you do when RFC 5661 says:
>
> >  The fetching of attributes containing file system location
> >  information SHOULD be performed using RPCSEC_GSS with integrity
> >  protection,
>
> Not much, since there is not much I can do about that.
>
> > And, you don’t now change to MUST use RPSEC_GSS?
>
> No I don't.   Currently use of AUTH_SYS is allowed and the working
> group has not made any decision to change that.
>
> > Well I think at a minimum you should do some 2119 language:
>
> OK, but note that this is a widely-deployed protocol and we are not
> in a position to invalidate deployment choices made in line with RFC5661,
> even if we think they were ill-advised.
>
> > 0) s16 (after the bullets): 2119 this should:
>
> If you are suggesting changing "should" to "SHOULD" in this parapgraph,
> I'm OK with making that change in -05, although I will raise the issue with
> the working group to check about existing implemtations.
>
> > 1) s16 (2nd para after the bullets): 2199 this SHOULD NOT:
>
> I intend to shift this to "SHOULD NOT"  in -05.
>
> > 2) s16 (last bullet): 2119 this should:
>
> Given that this bullet appears in a summary, I think the "should" is
> misleading.   Converting it to "SHOULD" would lead to recommemmending
> filtering without specifying the filtering to be done.  What I propose to
> do in -05 is replace "should be subect to filtering" by "is made subject to
> filtering as described above".
>
> > The use of requests issued without RPCSEC_GSS (i.e. using
> >  the known to be insecure AUTH_SYS), while undesirable and
> >  Insecure, may not be avoidable in all cases.
>
> While I approve of drawing more attention to the weaknesses of
> AUTH_SYS, I feel the use of the word "insecure" is too vague.
> "Insecure" covers a range of problems whereby traffic is either
> exposed to prying eyes, subject to corruption in transit, or acted
> upon without authentiction.   Given the context, I think we need to
> be clear about what the actual problem is even though AUTH_SYS,
> in what has to be considered a virtuoso performance :-), manages
> to acomplish the hat trick of protocol insecurity.
>
> So I propose writing this as follows:
>
> The use of requests issued without RPCSEC_GSS (i.e. using AUTH_SYS which
> has no provision to avoid corruption of data in flight), while undesirable
> and a potential security exposure, may not be avoidable in all cases.
>
>
> > It’s probably also worth discussing whether s14.3 should drop
> > support for includes id-sha1
>
> The text you are referring to was carried over from RFC5661 as-is since
> there was no issue known with it.
>
> Regarding the potential deletion of id-sha1, the issue, given that server
> support is currently REQUIRED, is whether there are clients using this who
> might be impacted by a change.   I'll check with the working group.
>
> > 4) s4.3 (1st sentence): Not sure the 2119-RECOMMENDED is needed.
>
> These are really OPTIONAL althouh the word "RECOMMENDED" is (confusingly)
> used.
> Will delete.
>
> > 5) s4.3 (penultimate para): Seems like r/should/SHOULD.
>
> It is probably the case that RFC5661 made a poor choice here.  However, I
> don't think we can change it now.
>
> > 10) s16 (3rd bullet): Why is requirement is caps?
>
> It's because I was under the misapprehension that statement that things
> were REQUIRED or RECOMMENDED could be referred to as "REQUIREMENTS" or
> "RECOMMENDATIONS".  It turns out not to be so.
>
> Will address nits 0)-4) and 6)-10) in -05.
>
> On Wed, Feb 27, 2019 at 12:38 PM Sean Turner <sean@sn3rd.com> wrote:
>
>> Reviewer: Sean Turner
>> Review result: Has Issues
>>
>> This draft updates NFSv4.1 to correct handling of the fs_locations and
>> fs_locations_info attributes; NFSv4.1 weighs in at 617 pages and this
>> draft weighs in a relatively spry 106; let’s say I was really, really
>> hoping
>> for some multi-page ASCII art, but also no pretty much all text.  The
>> draft does a good job of explaining what’s being replaced and why, but
>> I have to say that I did not check all of section pointers.  These
>> instructions will really help when work on a fully revised NFS RFC gets
>> going.  Unfortunately for me, I do not have NFSv4.1 in my head so let’s
>> just say that I did my best …
>>
>> Summary: This draft is probably worthy of some type of DISCUSS based
>> on the following:
>>
>> 0) The big issue being addressed in the security considerations is the
>> fact
>> that RPSEC_GSS is must support not must use and the other mechanism
>> referred to by RFC 5661 are:
>>
>> - AUTH_NONE - nada authentication
>>
>> - AUTH_SYS as described in Appendix A is known to be insecure due to
>>    the lack of a verifier to permit the credential to be validated.
>>    AUTH_SYS SHOULD NOT be used for services that permit clients to
>>    modify data.  AUTH_SYS MUST NOT be specified as RECOMMENDED or
>>    REQUIRED for any Standards Track RPC service.
>>
>> - AUTH_DH as mentioned in Sections 8.2 and 13.4.2 is considered
>>    obsolete and insecure; see [RFC2695].  AUTH_DH SHOULD NOT be used for
>>    services that permit clients to modify data.  AUTH_DH MUST NOT be
>>    specified as RECOMMENDED or REQUIRED for any Standards Track RPC
>>    service.
>>
>> So what do you do when RFC 5661 says:
>>   The fetching of attributes containing file system location
>>   information SHOULD be performed using RPCSEC_GSS with integrity
>>   protection,
>> And, you don’t now change to MUST use RPSEC_GSS?  Well I think at a
>> minimum you should do some 2119 language:
>>
>> 0) s16 (after the bullets): 2119 this should:
>>
>>   In light of the above, a server should present file system
>>   location entries that correspond to file systems on other servers
>>   using a host name.
>>
>> 1) s16 (2nd para after the bullets): 2199 this SHOULD NOT:
>>
>>    As a
>>    result, the client should not use such unverified location entries
>>    as a basis for migration, even though RPCSEC_GSS might be
>>    available on the destination.
>>
>> 2) s16 (last bullet): 2119 this should:
>>
>>   Where the use of the returned information cannot be
>>   avoided, it should be subject to filtering to eliminate the
>>   possibility that the client would treat an invalid address as
>>   if it were a NFSv4 server.
>>
>> And, I guess since AUTH_SYS is insecure can I suggest a friendly
>> amendment to the following sentence:
>>
>> OLD:
>>   The use of requests issued without RPCSEC_GSS (i.e. using
>>   AUTH_SYS), while undesirable, may not be avoidable in all
>>   cases.
>>
>> NEW:
>>
>>   The use of requests issued without RPCSEC_GSS (i.e. using
>>   the known to be insecure AUTH_SYS), while undesirable and
>>   Insecure, may not be avoidable in all cases.
>>
>> It’s probably also worth discussing whether s14.3 should drop
>> support for includes id-sha1.
>>
>>
>> These are the nits:
>>
>> 0) Update to use new 2119 paragraph:
>>
>>   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
>>   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
>>   "OPTIONAL" in this document are to be interpreted as described in BCP
>>   14 [RFC2119] [RFC8174] when, and only when, they appear in all
>>   capitals, as shown here.
>>
>> 1) s3.1 (wordy): r/since the
>>   ports to be used for various types of connections might be
>>   required to be different/since the
>>   ports to be used for various types of connections might be
>>   different.
>>
>> 2) s3.1 (missing period): r/Two such addresses support the use of clientid
>>   ID trunking, as described in [RFC5661]/Two such addresses support the
>> use of clientid
>>   ID trunking, as described in [RFC5661].
>>
>> 3) s4.2 (missing word): r/which may accessed/which may be accessed
>>
>> 4) s4.3 (1st sentence): Not sure the 2119-RECOMMENDED is needed.
>>
>> 5) s4.3 (penultimate para): Seems like r/should/SHOULD.
>>
>> 6) s4.5: r/present , is/present, is
>>
>> 7) s4.5: Note sure you need the parenthetical in the following:
>>   a server may (but is not required to)
>>
>> 8) s4.5.4: r/In the event that server failures,/In the event that
>> server fails,
>> or
>> r/In the event that server failures,/In the event of server failures,
>>
>> 9) s12.2.3: replace ietf.org with example.org (not supposed to use
>> real domains even if it is “ours”).
>>
>> 10) s16 (3rd bullet): Why is requirement is caps?
>>
>>